DESCRIPTION: Neuron cell death following cerebral ischemia from cardiac arrest or stroke is a major source of morbidity. Many lines of evidence suggest that disruption of calcium regulation may play a role in such injury. The proposed studies will test the novel hypothesis that ischemic neuronal damage is caused in part by excessive release of calcium from intracellular endoplasmic reticulum (ER) stores, leading to both a depletion of these stores and increased cytosolic calcium. Aim 1 will examine the role of ER calcium release in neuron culture models of cytotoxicity by agents that target ER stores, evaluating cell death, calcium release and the protective effects of dantrolene, which inhibits the ryanodine receptor (RYR)-mediated component of ER calcium release. Aim 2 will extend this approach to anoxic/aglycemic insults in the same in vitro preparations. The possible activation of a specific second messenger pathway involving nitric oxide, cGMP and cADP-ribose will be evaluated. Aim 3 will determine whether increased cytosolic calcium or depletion of ER pools contribute more importantly to cell death, and will evaluate the involvement of mitochondria. Aim 4 will extend the studies to an in vivo model and examine the effect of dantrolene, alone and in combination with a calcium channel blocker. These studies will provide information on novel mechanisms of ischemic neuronal death and on potential drug treatments that will be of clinical relevance.